There is a growing need for supplemental respiratory support for patients in the hospital and home environment. Positive pressure ventilation, in which a supply of pressurized air is delivered to the patient's airway, is often used. Positive pressure ventilation has been used to treat respiratory failure, respiratory insufficiency, and sleep apnea. There are a variety of patient interfaces that can be used to provide positive pressure ventilation including masks and nasal cannula. Mask interfaces are available for home and hospital use with many designs including nasal, oronasal (covering the nose and mouth), and full face masks.
Mask assemblies comprise a shell of rigid or pliable material (e.g., plastic) with a face-contacting cushion (e.g., a gel-filled bladder) that is held in place with headgear (e.g., straps). The shell provides the structure for the headgear connectors and elbow assembly. The cushion provides a seal against the patient's face creating a cavity around the airway through which positive pressure ventilation can be applied. Headgear connectors can be built into the mask or snapped onto the shell. Most headgear connectors center on the elbow assembly.
A common problem with existing mask technologies is the tendency for a broken or ineffective seal. Mechanical forces exerted on the mask when a patient changes position are often enough to break the seal. As the patient changes position, the headgear tends to slip between the patient's head and the bed, exerting a mechanical force on the mask in the opposite direction of the movement. This force tends to pull the mask, causing mask slippage. That slippage is often enough to break the seal. The noise and discomfort, from the broken seal, is usually enough to wake or stir the patient. The patient or attendant then needs to refasten the mask to obtain an effective seal.
If a mask is used for the administration of Continuous Positive Airway Pressure (“CPAP”) treatment for the condition of obstructive sleep apnea, such a leak can drop the pressure, and amount of breathable air, provided to the mask wearer. Thus, treatment becomes ineffective. If the patient does not wake as a result of the leak, the patient can go potentially without treatment for a long period of time. Alternatively, if the mask is used for the treatment of respiratory insufficiency in a hospital environment, the leak will induce alarms from the ventilation device that will alert hospital staff. While there is minimal risk for the patient to be without treatment for a long period of time, the patient will still have disrupted sleep.
There have been numerous attempts, by different manufacturers, to design a mask that will maintain equal pressure on both sides of the mask when the head is rotated from side to side. The earliest attempts resulted in masks that were uncomfortable to wear, reducing the rate of patient compliance. In recent years, manufacturers have focused on comfort when designing masks that can maintain an effective seal during movement. Manufacturers have tried to combat the leak issue by increasing the size of the cushion, changing its shape, or using material (e.g., a gelatinous material inside a thin bladder) that easily conforms to the patient's face. An increased cushion size, for example, can increase comfort and flexibility of the mask allowing it to maintain an effective seal by conforming to the patient's movements. Other manufactures have tried to alter the structure of the mask shell or the materials used to make the headgear connector.
One example of a mask that relies on a larger cushion size is the ResMed Mirage™ SoftGel nasal mask as described in U.S. patent application Ser. No. 12/736,980, Publication No. 2011/0162654, filed by Carroll et al. The Mirage™ mask design includes a gel cushion with two layers. The internal layer of the gel is softer than the outer layer. The outer layer provides structure for the cushion and comprises the face contacting portion. There is a plastic frame attached to the cushion that snaps into the mask shell. The frame fits into grooves on the mask contacting portion of the gel cushion. The cushion provides flexibility, allowing the Mirage™ mask to move somewhat with the patient. Its frame, however, does not hold the cushion securely, especially when a wearer tosses and turns while sleeping. During such movement, the cushion can give way when the patient moves creating a leak between the frame and cushion. This design also contributes to excessive mask weight, which can lead to reduced patient comfort.
Another invention attempts to reduce leaks by adding flexibility within the mask structure. Respironics' TrueBlue™ nasal mask combines a few of the manufacturer's technologies. The mask design relies on an accordion shaped tube (a.k.a. “freeform spring”) between the mask shell and elbow to provide flexibility within the mask structure. It has a “3-point” headgear connector anchored to the mask, with an elbow in the center. There are two points with slots to receive the headgear straps on either side of the elbow. There is one point at the top of the connector attached to a forehead pad with two slots for headgear straps. The headgear connector is rigid, but the mask shell is designed to flex easily, alleviating some tension between the headgear connector and headgear straps. The headgear attaches to talons that snap into the headgear connector, which allows the headgear to have added flexibility. While the freeform spring design may withstand mechanical forces from movement during sleep, the elongated mask shape may cause the patient to have to breathe out with more force to expel unwanted carbon dioxide. A buildup of carbon dioxide in the TrueBlue™ mask could be harmful to the patient.
Another invention attempts to reduce leaks by using a flexible headgear connector (a.k.a. “glider strap”). Fisher & Paykel's Flexfit™ 432 full face mask incorporates a wire headgear connector that snaps in to the front of the mask. The glider strap slides from side to side, providing freedom of movement while maintaining a seal. The sliding movement allows the headgear connector to withstand the mechanical forces from movement when the head is rotated side to side. One issue with the Flexfit™ 432 design is the ease with which the headgear connector can be dislodged from the mask. Once the headgear connector becomes dislodged, it is difficult to reattach.
Accordingly, it is a primary object of the present invention to a headgear connector for CPAP masks that can articulate three dimensionally (i.e., in the X-Y-Z planes) with the force incurred during a patient's movement, thus maintaining an effective seal.
It is another general object to provide a headgear connector design suitable for different types of respiratory masks.
It is another general object to provide a headgear connector, commensurate with the above-listed objects, which is safe and durable to use.